Methods and devices for treatment of obstructive sleep apnea

ABSTRACT

A pharyngeal retractor device and implantation methods are provided for use in the treatment of obstructive sleep apnea. The device includes a retracting element and a tissue engaging element that promotes tissue ingrowth around or onto the retracting element. The device is implanted in tissue space beneath the pharyngeal wall to alter the shape of the wall. The device may be implanted through the oral cavity alone or by using a trocar or a hand-held delivery system to deliver the device through the pharyngeal wall. Alternatively, the device may be implanted using an open, direct visualization approach from the side of a patient&#39;s neck.

FIELD OF THE INVENTION

The present invention relates generally to the surgical treatment ofobstructive sleep apnea, and more particularly, to the use of implantsto prevent pharyngeal wall collapse or to provide altered airwaygeometries to prevent possible airway obstruction during sleep.

BACKGROUND OF THE INVENTION

Several forms of sleep apnea have been identified. Obstructive sleepapnea (OSA) is caused by a blockage of the airway, usually when the softtissue in the throat collapses and closes during sleep. Less commonforms of sleep apnea include central sleep apnea (CSA), wherein theairway is not blocked but the brain fails to signal the muscles tobreathe, and mixed apnea which, as the name implies, is a combination ofOSA and CSA.

As shown in FIG. 1 a, an air passage 140 a of a patient 101 a is openwhile the patient is in the awake state. The soft tissue components,including the soft palate 130 a and the pharyngeal walls 132 a of theair passage are supported by the underlying musculature to maintain thepassageway in the open condition. During an obstructive sleep apneaevent, illustrated in FIG. 1 b, the air passage 140 b of a patient 101 bis partially or completely blocked by surrounding soft tissue 130 b, 132b, which has collapsed due to the relaxation of the supportingmusculature and has been displaced during sleep by gravity or otherforces.

With each apnea event, the brain briefly arouses the sleeping person inorder to resume breathing, but sleep is consequently extremelyfragmented and of poor quality. Untreated, sleep apnea can cause highblood pressure, cardiovascular disease, memory problems, weight gain,impotency, and headaches. Moreover, untreated sleep apnea may beresponsible for job impairment, motor vehicle crashes, and maritaldiscord.

According to the National Institutes of Health, sleep apnea is verycommon, as common as adult diabetes, and affects more than twelvemillion Americans. The factors that increase the risk of having OSAinclude being male, overweight, and over the age of forty, but sleepapnea can strike anyone at any age, even children. Because of the lackof awareness by the public and healthcare professionals, the vastmajority of patients remain undiagnosed and therefore untreated, despitethe fact that this serious disorder can have significant consequences.

Attempts to provide an effective treatment for obstructive sleep apneahave yielded unsatisfactory results. For example, electrical stimulationof the soft palate has been suggested to treat snoring and obstructivesleep apnea. Such a teaching is found in Schwartz et al., “Effects ofelectrical stimulation to the soft palate on snoring and obstructivesleep apnea,” J. Prosthetic Dentistry, pp. 273-281 (1996). Devices toapply electrical stimulation are described in U.S. Pat. Nos. 5,284,161and 5,792,067. Electrical stimulation to treat sleep apnea is alsodiscussed in Wiltfang et al., “First results on daytime submandibularelectrostimulation of suprahyoidal muscles to prevent night-timehypopharyngeal collapse in obstructive sleep apnea syndrome,”International Journal of Oral & Maxillofacial Surgery, pp. 21-25 (1999).Such devices are appliances requiring patient adherence to a regimen ofuse as well as subjecting the patient to discomfort during sleep andrepeated arousals during deep sleep.

Continuous Positive Airway Pressure (CPAP) has recently been adopted asa useful, albeit cumbersome, means of preventing sleep apnea. CPAPdelivers air into the airway through a specially designed nasal mask orpillows. The mask does not breathe for the patient; the flow of aircreates enough pressure when the patient inhales to keep the airwayopen. In effect, a pneumatic splint is formed in the airway. CPAP isconsidered the most effective non-surgical treatment for the alleviationof snoring and obstructive sleep apnea. Compliance, however, is only50%, as patients complain about discomfort from the mask, hoses, etc.and that the equipment requires maintenance. Additionally, patientscomplain of discomfort such as bloating, nasal drying, and dry eyes.

Surgical treatments have also been employed. One such treatment isuvulopalatopharyngoplasty (UPPP). UPPP is discussed, for example, inHarries et al., “The surgical treatment of snoring,” Journal ofLaryngology and Otology, pp. 1105-1106 (1996), which describes removalof up to 1.5 cm of the soft palate. The use of UPPP in the treatment ofsnoring is assessed in Cole et al., “Snoring: A review and aReassessment,” Journal of Otolaryngology, pp. 303-306 (1995). In thatprocedure, about 2 cm of the trailing edge of the soft palate is removedthrough the use of a scalpel, laser or other surgical instrument,thereby reducing the tendency of the soft palate to flutter between thetongue and the pharyngeal wall of the throat. The procedure isfrequently effective to alleviate snoring but has demonstrated limitedeffectiveness in moderate or severe apnea. The procedure is painful andfrequently results in undesirable side effects. In particular, thereduction of the soft palate compromises the ability of the soft palateto seal off nasal passages during swallowing and speech. In an estimated25% of uvulopalatopharyngoplasty patients, fluid escapes from the mouthinto the nose while drinking.

Uvulopalatopharyngoplasty (UPPP) may involve lasting discomfort. Forexample, scar tissue on the soft palate may present a continuingirritant to the patient. In addition, UPPP is not reversible and mayinduce adverse side effects not justified by the benefits of thesurgery. Furthermore, UPPP is targeted to the correction of deficienciesassociated with the palate only and does not address issues associatedwith the collapse of the tongue and lateral pharyngeal walls.

Radiofrequency ablation of the soft palate, or Somnoplasty^(SM), issimilar in concept to the Laser Assisted Uvulopalotopharyngoplasty(LAUP), although a different energy source is used, and thermal lesionsare produced within the tissues, rather than using a laser to ablate thetissue surface. For that reason, radiofrequency ablation appears to begrowing in popularity as an alternative to LAUP. The Somnoplasty^(SM)device is approved by the U.S. Food and Drug Administration (FDA) forradiofrequency ablation of palatal tissues for simple snoring andradiofrequency ablation of the base of the tongue for OSA. In somesituations, radiofrequency ablation of the soft palate and base oftongue are performed together as a multi-level procedure. To date, thetreatments alone or in combination have failed to provide relief to morethan 50% of patients.

Another device intended to treat snoring or obstructive sleep apnea iscomprised of several braided PET cylinders that are implanted to makethe tissues of the tongue or uvula more rigid and less prone todeflection against the pharyngeal wall. The Pillarm Palatal ImplantSystem, marketed by Restore Medical of St Paul, Minn., is an implantabledevice that has been cleared by the FDA 510(k) process. The device is acylindrical-shaped segment of braided polyester filaments that ispermanently implanted submucosally in the soft palate. The labeledindication of the device is as follows: “The Pillar™ Palatal ImplantSystem is intended for the reduction of the incidence of airwayobstructions in patients suffering from mild to moderate OSA(obstructive sleep apnea).” The device has been associated with a numberof adverse side effects, including extrusion, infection, and patientdiscomfort.

The Repose™ device, marketed by Influent Medical LLC of Concord, N.H.,involves the use of a titanium screw that is inserted into the posterioraspect of the mandible at the floor of the mouth. A loop of suture ispassed through the tongue base and attached to the mandibular bonescrew. The Repose™ procedure achieves a suspension or hammock of thetongue base making it less likely for the base of the tongue to collapseagainst the posterior pharyngeal wall during sleep. The reportedduration of beneficial effects afforded by the implant is less than ayear. Due to the high activity of the tongue during wakefulness, thesuture component of this device has been shown in some cases to act as a“cheese cutter” to the tongue, causing device failure and requiringsubsequent removal.

Magnets have also been considered as implants for the treatment ofobstructive sleep apnea. These devices are currently being evaluated inclinical trials. One serious complication than can potentially occurwith these implants is implant migration or flipping of the magnetswhich can cause acute airway closure.

In summary, electrical stimulation of the musculature within the airwayis ineffective since it arouses the patient from deep sleep. CPAPeffectively manages OSA but has a very low patient compliance (less than50% of patients continue the treatment). Surgical techniques andimplants have also been evaluated, yet still do not provide asatisfactory and lasting solution. No one device seems capable oftreating the multi-causal problem of obstructive sleep apnea. What isneeded are methods and devices that reduce the burden of managingobstructive sleep apnea through a minimally invasive approach thatprovides long term and effective results. Ideally, the treatment shouldbe adjustable and removable if necessary. The inventions describedherein provide such treatments that offer long-term relief of OSA.

SUMMARY OF THE INVENTION

The present invention is directed to systems and methods for treatingobstructive sleep apnea. One embodiment of the invention is a method forsurgically treating obstructive sleep apnea, comprising the step ofimplanting a device into tissue space located beneath a pharyngeal wallto alter a shape of the pharyngeal wall. In one embodiment, the deviceretracts or alters the shape of the pharyngeal wall to resist collapse.In another embodiment, the device alters the geometry of the airway toprevent complete obstruction of the pharyngeal tissues during sleep.

The device is a retractor that has a self-supporting tissue engagingelement that controls the position of the soft tissues beneath thepharyngeal wall during sleep and allows for tissue ingrowth. The tissueengaging element may, for example, be a biocompatible mesh or othersuitable porous fabric. The tissue engaging element may be made throughtypical processing means including, but not limited to, fiber knitting,weaving, braiding, non-woven production, expansion methods (such asePTFE) or perforation of film type products, melt blowing, extrusion,carding, or injection molding. The retractor is generally of a “sheetlike” or planar shape, with the width, length and thickness dimensionsof the retractor typically not equal.

The retractor may be introduced orally and implanted through thepharyngeal wall into the tissue beneath the pharyngeal wall. Theretractor may alternatively be introduced through a side of a patient'sneck. The retractor is placed within the soft tissues of the neck,either within tissue planes or crossing them, as deemed appropriate bythe surgeon to produce sufficient retraction or alteration of the lumenof the affected region of the airway.

One embodiment of the invention is a device for altering a shape of apharyngeal wall by implantation of the device in tissue beneath thepharyngeal wall. The device comprises a retracting element having aconstrained configuration and an unconstrained configuration differentfrom the constrained configuration, and a tissue engaging elementconnected to the retracting element, the tissue engaging element adaptedfor engaging the tissue beneath the pharyngeal wall. A shape of thepharyngeal wall is altered when the retracting element reverts from theconstrained configuration to the unconstrained configuration.

Another embodiment of the invention is a method for surgically treatingobstructive sleep apnea. The method includes the steps of delivering animplantable device into tissue located beneath a pharyngeal wall, andengaging the tissue beneath the pharyngeal wall with the implantabledevice to alter a shape of the pharyngeal wall.

The invention is further embodied by a system for treating obstructivesleep apnea by altering a shape of a pharyngeal wall. The systemcomprises an implantable device including a tissue engaging element anda retracting element, and a hand-held delivery system comprising ahand-piece, an actuating lever moveably connected to the hand-piece, ashaft extending distally from the hand-piece, a housing disposed at adistal end of the shaft for storing at least one implantable device, anda deployment device activatable by the lever for deploying theimplantable device through the pharyngeal wall into tissue space locatedbeneath the pharyngeal wall so as to alter a shape of the pharyngealwall.

Another embodiment of the invention is a device for retracting apharyngeal wall. The device includes an elongate fibrous member having acentral portion for engagement with the pharyngeal wall, and havingfirst and second retracting portions extending from the central portion,each of the first and second retracting portions having features forengaging tissue in the neck and exerting a tensile retraction force onthe central portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are schematic cross-sectional representations of apatient's upper airway.

FIG. 2 is a schematic cross-sectional representation of a patient'supper airway.

FIG. 3 a is a cross-sectional view of a pharyngeal wall showing severalsuperimposed states of the wall.

FIG. 3 b is a cross-sectional view of a pharyngeal wall showing twopharyngeal retractors implanted according to one embodiment of theinvention.

FIG. 4 is a plan view of a trocar according to one embodiment of theinvention.

FIG. 5 is a plan view of a pharyngeal retractor implant system accordingto another embodiment of the invention.

FIGS. 6 a-6 f are views of several pharyngeal retractors according tovarious embodiments of the invention.

FIG. 7 is a schematic representation of a patient's upper airway showinga pharyngeal retractor implanted according to one embodiment of theinvention.

FIG. 8 is a schematic representation of a patient's upper airway showinga pharyngeal retractor implanted according to one embodiment of theinvention.

FIG. 9 is a schematic transverse cross-section of a patient's head at alevel below the temporal styloid process, showing one embodiment of theinvention.

FIG. 10 is a schematic representation of a patient's head showing apharyngeal retractor implantation method according to one embodiment ofthe invention.

FIG. 11 a is a schematic cross-sectional representation of a patient'supper airway showing two pharyngeal retractors during an implantationprocess according to one embodiment of the invention.

FIG. 11 b is a schematic cross-sectional representation of a patient'supper airway showing the two pharyngeal retractors of FIG. 11 a afterimplantation.

FIG. 12 a is a schematic cross-sectional representation of a patient'supper airway showing two pharyngeal retractors during an implantationprocess according to another embodiment of the invention.

FIG. 12 b is a schematic cross-sectional representation of a patient'supper airway showing the two pharyngeal retractors of FIG. 12 a afterimplantation.

FIG. 13 is a cross-sectional representation of a patient's upper airwayshowing a pharyngeal retractor according to another embodiment of theinvention.

DETAILED DESCRIPTION

The present invention is directed to a device and method of implantationthat can be used to treat obstructive sleep apnea. The device can beimplanted into tissue beneath the pharyngeal wall using severalimplantation methods described herein. The term “beneath the pharyngealwall” refers to a space beneath the pharyngeal wall that does not existnaturally but is formed during the implantation step. The newly formedspace allows the device to be implanted next to the back of thepharyngeal wall (the side that does not face the airway) and against theprevertebral fascia and musculature such as the longus capitus muscles.The device, referred to herein as a retractor or simply as the “device,”may include a flexible backing or arch-shaped retracting elementattached to a tissue engaging element. The device is used to alter acharacteristic of the pharyngeal wall. For example, the device mayprovide additional retraction means on the lateral pharyngeal walls ormaintain an altered shape of the airway. The device of the inventionprovides retraction or support of the pharyngeal walls to allow air toflow past any obstruction that may be apparent if the pharyngeal wallsare collapsed. It may also be used to change the shape of the pharyngealairway.

FIG. 2 illustrates a cross-section of a patient's head with anatomicalstructures such as the nasal sinuses (N), bone (B) of the hard palate(HP), soft palate (SP), mouth (M), tongue (T), trachea (TR) epiglottis(EP), esophagus (ES) and posterior pharyngeal wall (PPW). The lateralpharyngeal walls (not shown in this illustration) are, as the nameimplies, lateral to the posterior pharyngeal wall. According to imagingstudies on CPAP users described by Schwab et al., “Upper airway and softtissue changes induced by CPAP in normal subjects,” Am. J. Respir. Crit.Care Med., Vol 154, No. 4, October 1996, 1106-1116, the lateralpharyngeal walls are more “compliant” than the soft palate and tongue.Those studies provide evidence that the lateral pharyngeal walls play animportant role in mediating upper airway caliber. In certain disclosedembodiments, the intent of the implantable devices described herein isto retract the pharyngeal walls laterally. The lateral retraction servesto prevent collapse of these soft tissue structures and to maintain anairway for the patient, particularly when the diaphragm descends duringinhalation and causes excessive negative pressure that might act tocollapse the pharyngeal walls. In certain other disclosed embodiments,the intent of the implantable device is to provide altered geometries ofthe airway during inhalation that are unable to occlude due tomismatched geometries between the mating tissues, more particularly thebase of the tongue and the posterior and or lateral pharyngeal walls.

FIG. 3 a illustrates a cross-section of the pharynx at the oropharyngeallevel, including the posterior pharyngeal wall (PPW) and lateralpharyngeal walls (LPW). The oropharynx is shown in solid lines in itsdistended (retracted) state, and is shown in dashed lines in a normalrelaxed state and in a partially collapsed state. As shown in FIG. 3 b,a pair of implantable devices 301 a, 301 b in accordance with theinvention causes the left (LLPW) and right (RLPW) lateral walls of thepharynx to resist the negative pressure produced by the descendingdiaphragm, thereby keeping the airway open. Subsequent tissue engagementwith the implantable device and tissue ingrowth 302 into the deviceserve to secure the mesh strip, and therefore, to stabilize theretracted state.

One embodiment of the invention is an implantable device that isreleasably attached to at least one trocar. FIG. 4 illustrates a trocar400 having a distal end 401 and a handle 402 on the proximal end. Thedistal end 401, with the implantable device attached, is passed throughthe pharyngeal wall and into the tissue underneath the pharyngeal wall.The implantable device is then placed in the formed space beneath thepharyngeal wall.

The trocar 400 may optionally have a Doppler probe (not shown) thatallows detection of blood flow in any arterial structures located nearthe target tissues. The probe may be embedded within the distal tip 401so as to help navigate the tissue and avoid damaging blood vessels,particularly when an approach is utilized whereby the implantable deviceis installed across multiple tissue planes within the affected regionsof the neck.

In addition to the minimally invasive approach using a trocar, thedevice may alternatively be placed beneath the pharyngeal wall using anopen, direct approach to the pharyngeal wall from the side of apatient's neck. A single device or more than one of the devices can beused to treat the patient.

FIG. 5 illustrates an exemplary attachment of a mesh device 500 to thetrocar 400. The mesh device 500 is fixed to a proximal end of a plastictrocar sleeve 502 that covers the distal end of the trocar. The fixationof the mesh to the end of the plastic trocar sleeve can be achievedthrough the use of wrapping, welding, gluing, tying, clips or othersuitable means. In one embodiment, the device 500 is a mesh made frompolypropylene or another porous biocompatible material selected for itstissue engaging properties.

In the embodiment shown, the implantable device 500 is covered by aprotective sheath 501. Polymers such as expanded polytetrafluoroethylene(ePTFE), polyethylene terephalate (PET), PVDF, polyesters, polyolefins,silicones or polyurethanes are utilized in the construction of theprotective sheath. The materials and construction techniques of theprotective sheath are chosen so as to minimize friction and engagementof the sheath with surrounding tissue. The purpose of the protectivesheath 501 is to minimize tissue drag on the implantable device duringinsertion and to prevent any abrasion or irritation of non-targettissues during placement of the device.

In use, the distal end 401 (FIG. 4) of the trocar penetrates thepharyngeal wall at or near a lateral or posterior portion of the wall.If necessary, the insertion of the trocar may be facilitated through theuse of an incision made just prior to the implantation step. The site ofincision and orientation of the device will be determined by the surgeonand will be dependent on the individual patient anatomy and the site ofpharyngeal collapse. Alternatively, the trocar 400 may have a sharpenededge at its distal end 401 for piercing the mucosal surface of thepharyngeal wall. The trocar is then used to pass the mesh device 500through the pharyngeal wall and to deposit the device in the tissuebeneath the pharyngeal wall. In one embodiment, after penetrating thepharyngeal wall and passing through the tissue beneath the pharyngealwall, the trocar tip is passed through the pharyngeal wall again at asecond location, passing from underneath the wall to within the airway.The mesh is then drawn through the tissue using the plastic trocarsleeve, with the protective sheath surrounding the mesh to protect thetissue. The plastic trocar sleeve and the protective sheath are thenremoved. If the pharyngeal retractor is longer than necessary, it istrimmed to length while under slight tension to reduce the length thatremains within the pharyngeal wall. The incisions in the pharyngeal wallare then closed with suture, clips, or biocompatible tissue adhesive.

FIG. 6 a illustrates one embodiment of an implantable device accordingto the invention. The device comprises a tissue engaging element shownin FIG. 6 a as a length of mesh 600. In the embodiment of FIG. 6 a, noother material is attached or associated with the mesh. The tissueengaging element is implantable into the space beneath the pharyngealwall. The element is constructed to frictionally or otherwise engagesurrounding tissue upon implantation, and to thereby resist movementafter placement within the tissue.

The biocompatible tissue engaging element 600 is further receptive totissue ingrowth in the form of scar tissue that embeds during healingand becomes integrated with the mesh. That scar tissue reinforces theoverall tissue mass in which the tissue engaging element is implanted.The element may encourage structural ingrowth of surrounding tissue, andmay also encourage cellular ingrowth of tissue.

Many medical textile designs are known to those skilled in the art ofmaking mesh, fabrics, non-wovens, etc. for hernia repair. Medicaltextile products are based on fabrics, of which there are four types:woven, knitted, braided, and nonwoven. The first three of these are madefrom yarns, whereas the fourth can be made directly from fibers, or evenfrom polymers such as Gore-Tex®-based products or electrostatically spunmaterials from polyurethane. There is, therefore, a hierarchy ofstructure: the performance of the final textile product is affected bythe properties of polymers whose structures are modified at between twoand four different levels of organization.

Of the many different types of polymers, only a few can be made intouseful fibers. This is because a polymer must meet certain requirementsbefore it can be successfully and efficiently converted into a fibrousproduct. For example, the polymer chains should be linear, long, andflexible. Side groups of the polymers should be simple, small, or polar.Polymers should be dissolvable or meltable for extrusion. Chains shouldbe capable of being oriented and crystallized.

Common fiber-forming polymers include cellulosics (linen, cotton, rayon,acetate), proteins (wool, silk), polyamides, polyester (PET), olefins,vinyls, acrylics, polytetrafluoroethylene (PTFE), polyphenylene sulfide(PPS), aramids (Kevlar, Nomex), and polyurethanes (Lycra, Pellethane,Biomer). Each of these materials is unique in chemical structure andpotential properties. For example, among the polyurethanes is anelastomeric material with high elongation and elastic recovery, whoseproperties nearly match those of elastin tissue fibers. Thismaterial—when extruded into fiber, fibrillar, or fabric form—derives itshigh elongation and elasticity from alternating patterns of crystallinehard units and noncrystalline soft units.

Although several of the materials mentioned above are used intraditional textile as well as medical applications, various polymericmaterials—both absorbable and nonabsorbable—have been developedspecifically for use in medical products.

The reactivity of tissues in contact with fibrous structures variesamong materials and is governed by both chemical and physicalcharacteristics. Absorbable materials typically excite greater tissuereaction, a result of the nature of the absorption process itself. Amongthe available materials, some are absorbed faster (e.g., polyglycolicacid, polyglactin acid) and others more slowly (e.g., polyglyconate).Semiabsorbable materials such as cotton and silk generally cause lessreaction, although the tissue response may continue for an extendedtime. Nonabsorbable materials (e.g., nylon, polyester, polypropylene)tend to be inert and to provoke the least reaction. To minimize tissuereaction, the use of catalysts and additives is carefully controlled inmedical-grade products.

As discussed, of the many types of polymers, only a few can be made intouseful fibers that can then be converted into medical textile products.To make fibers, polymers are extruded by wet, dry, or melt spinning andthen processed to obtain the desired texture, shape, and size. Throughcareful control of morphology, fibers can be manufactured with a rangeof mechanical properties. Tensile strength can vary from textile values(values needed for use in typical textile products such as apparel) of2-6 g/d (gram/denier) up to industrial values (values typical ofindustrial products such as tire cords or belts) of 6-10 g/d. Forhigh-performance applications, such as body armor or structuralcomposites, novel spinning techniques can produce fibers with strengthsapproaching 30 g/d. Likewise, breaking extension can be varied over abroad range, from 10-40% for textile to 1-15% for industrial and100-500% for elastomeric fibers.

Fibers or filaments are converted into yams by twisting or entanglingprocesses that improve strength, abrasion resistance, and handling. Yamproperties depend on those of the fibers or filaments as well as on theangle of twist. Yarns are interlaced into fabrics by various mechanicalprocesses, including weaving, knitting, and braiding. There are threeprevalent fabric structures used for medical implants or sutures: woven,in which two sets of yams are interlaced at right angles; knitted, inwhich loops of yam are intermeshed; and braided, in which three or moreyams cross one another in a diagonal pattern. Knitted fabrics can beeither weft or warp knit, and braided products can include tubularstructures, with or without a core, as well as ribbon.

There are also numerous medical uses for nonwoven fabrics (wipes,sponges, dressings, gowns), made directly from fibers that areneedle-felted, hydroentangled, or bonded through a thermal, chemical, oradhesive process. Nonwovens may also be made directly from a polymer.Expanded polytetrafluoroethylene (ePTFE) products such as sutures andarterial grafts and electrostatically spun polyurethane used as tubularstructures are examples of medical applications of polymer-to-fabricnonwovens.

The properties of fabrics depend on the characteristics of theconstituent yams or fibers and on the geometry of the formed structure.Whether a fabric is woven, knitted, braided, or nonwoven will affect itsbehavior. Fabrics that are woven are usually dimensionally very stablebut less extensible and porous than the other structures. Onedisadvantage of wovens is their tendency to unravel at the edges whencut squarely or obliquely for implantation. However, the stitchingtechnique known as a Leno weave—in which two warp threads twist around aweft—an substantially alleviate this fraying or unraveling.

Compared with woven fabrics, weft-knitted structures are highlyextensible, but they are also dimensionally unstable unless additionalyarns are used to interlock the loops and reduce the extension whileincreasing elastic recovery. Warp-knitted structures are extremelyversatile, and can be engineered with a variety of mechanical propertiesmatching those of woven fabrics. The major advantage of knittedmaterials is their flexibility and inherent ability to resist unravelingwhen cut. A potential limitation of knitted fabrics is their highporosity, which—unlike that of woven fabrics—cannot be reduced below acertain value determined by the construction. As a result, applicationsrequiring very low porosity usually incorporate woven materials.

Typically employed in cords and sutures, braided structures can bedesigned using several different patterns, either with or without acore. Because the yams criss-cross each other, braided materials areusually porous and may imbibe fluids within the interstitial spacesbetween yarns or filaments. To reduce their capillarity, braidedmaterials are often treated with a biodegradable (polylactic acid) ornonbiodegradable (Teflon®) coating. Such coatings also serve to reducechatter or noise during body movement, improve hand or feel, and helpposition suture knots that must be transported by pressure from asurgeon's finger from outside the body to the wound itself.

The properties of nonwoven fabrics are determined by those of theconstituent polymer or fiber and by the bonding process. For instance,expanded PTFE products can be formed to meet varying porosityrequirements. Because of the expanded nature of their microstructure,these materials compress easily and then expand—a suture, for example,can expand to fill the needle hole made in a tissue—allowing for tissueingrowth in applications such as arterial and patch grafts.Polyurethane-based nonwovens produce a product that resemblescollagenous material in both structure and mechanical properties,particularly compliance (extension per unit pressure or stress). Theporosity of both PTFE- and polyurethane-derived nonwovens can beeffectively manipulated through control of the manufacturing processes.

In one embodiment of the invention, the tissue engaging element utilizedin the implantable device is fabricated by warp knitting a monofilamentpolypropylene yarn that is approximately 3 to 6 mils in diameter. In oneexemplary embodiment, the yam is 3.5 mils in diameter. In thisembodiment, the knitted mesh preferably has 40-80 courses per inch and7-11 wales per inch. Other designs of medical textiles may also be used.

In addition to the polymeric fibers described above, non-polymericfibers may be used in constructing woven, braided, knitted and non-wovenfabrics for use in the invention. For example, nitinol or stainlesssteel fibers may be used alone or in combination with other fibers suchas polymeric fibers to construct a tissue engaging element havingaltered retraction properties.

A perforated film-type product (not shown) may alternatively be used infabricating the tissue engaging element. In that embodiment, a polymerfilm is perforated with a plurality of holes to engage tissue and toallow tissue ingrowth. The size and spacing of the holes may beoptimized for those functions. Further, the size and spacing of theholes may be varied over the film to promote greater tissue engagementin certain locations on the film.

The tissue engaging element may comprise a film having other types oftissue engaging features, alone or in combination with perforations. Forexample, the film may comprise corrugations, dimples, knurling or otherembossed, molded or machined relief patterns that engage tissue that ispressed against the tissue engaging element. Full or partialperforations may include raised edges that engage surrounding tissue.

A retracting element shown in FIG. 6 b, such as a flexible backing orarch 601, may be used. The retracting element 601 is fabricated from abiocompatible material such as stainless steel, nitinol, silicone,polyethylene, polytetrafluoroethylene, or polypropylene. The retractingelement is preferably capable of withstanding a large number of flexcycles without fatigue failure because the element undergoes a straincycle with each movement of the pharyngeal wall, such as in swallowingand speaking. The retracting element 601 may be produced with athree-dimensional geometry in order to exert specific directional forceswhen deployed that change one or more characteristics of the pharyngealwall, as described in more detail below.

In another embodiment, the retracting element may be substantiallynon-flexible. A non-flexible retracting element may be fabricated fromtitanium, stainless steel or ceramic. An implantable device including anon-flexible retracting element may be used to maintain a shape of apharyngeal wall to prevent collapse.

A retracting element 601 may be attached to a tissue engaging element600, as shown in FIG. 6 c, in another embodiment of the invention. Theattachment may be by adhesive, suture, clips, staples, screws, oranother fastening means such as ultrasonic welding. As noted above, thetissue engaging element engages surrounding tissue after implantationand promotes tissue ingrowth, becoming permanently integrated with thesurrounding tissue. As a result, the retracting element 601 becomespermanently fixed in position beneath the pharyngeal wall and will notmigrate. The result is that the pharyngeal wall is less likely tocollapse during sleep and produce an obstruction to breathing.

In an alternative embodiment of the invention, the tissue engagingelement, the retracting element, or both can be at least partiallyfabricated from resorbable synthetic polymers such as polylactide,polyglactide, polydioxanone, polycaprolactone, or co-polymers thereof.The long-term shape of the soft tissue is provided through the presenceof the tissue formed around and through the tissue engaging element asthe absorbable component of the implant is resorbed.

FIGS. 6 d-6 f are cross-sectional views through several embodiments of aimplantable device of the invention incorporating both a mesh tissueengaging element and an arch-shaped retracting element. FIG. 6 d is across-sectional view of the device of FIG. 6 c, wherein one side of thetissue engaging element 601 is attached to a retracting element 601. Thetissue engaging element 601 may be attached through the use ofadhesives, such as cyanoacrylates, silicones and hot melt polymers. Theadhesives may be absorbable or non-absorbable. The tissue engagingelement may alternatively be attached through the use of mechanicalfixation means such as sutures and clips.

Alternatively, as shown in FIG. 6 e, the retracting element may beproduced with a reduced width and then passed through or woven into themesh component. The figure shows an embodiment wherein the flexible archis encased within a sleeve 603 comprising the tissue engaging element.The retracting element may alternatively comprise holes, slots or otherfeatures (not shown) allowing the retracting element to be interwoveninto the fabric of the tissue engaging element.

In the embodiment shown in FIG. 6 f, the mesh 600 is attached to tworetracting elements 601 a and 601 b, one on each side of the meshcomponent. All of the embodiments shown may be used to provide sustainedretraction or shaping of the pharyngeal wall.

Optionally, image-enhancing substances such as radio-opaque orultrasonically sensitive materials can be layered onto any of thesurfaces of the pharyngeal retractor to aid in imaging of the deviceduring and after deployment. In another embodiment, anti-microbialagents such as triclosan or antibiotics, or pain management medicamentsare applied or coated to one or more surfaces of the components thatcomprise the pharyngeal retractor prior to deployment. Alternatively,the agents may be included in the polymers during the fabricationprocesses through extrusion, blending, casting, solvent mixing or othertypical polymer processing means. The agents may be included within anabsorbable component to provide controlled or profiled release of thesubstances during wound healing.

Orientation of the implantable device in the patient may be selecteddepending on the particular patient anatomy. For example, an elongateddevice may be placed so that the device ends are in the same plane asthe pharynx or in a plane parallel to the pharyngeal axis (PAX), asillustrated by the device 700 shown in FIG. 7; i.e., so that alongitudinal axis of the device is parallel to the pharyngeal axis.Alternatively, the mesh strip may be placed perpendicular to thepharyngeal axis (PAX), as illustrated by the device 800 shown in FIG. 8.In that case, the longitudinal axis of the mesh strip is perpendicularto the pharyngeal axis. In either case, the implantable device (with orwithout a retracting element) is placed by a surgeon in such a way so asto change the shape of the pharyngeal walls to prevent collapse duringinhalation.

In addition to placing the implantable device using a trocar in aminimally invasive approach, the device of the invention may also beplaced underneath the pharyngeal wall using an open, directvisualization approach to the pharynx from the side of a patient's neck.A similar approach to the tissue space underneath the pharyngeal wall isused to perform cervical spinal disc replacement. That approach may beused in the present invention on an outpatient basis or one nighthospital stay, for example.

The implantable device of the invention may be a retractor 900 (FIG. 9)that is produced as or includes a fibrous element 905 with tissueengaging features 910. The tissue engaging features may be directionalfrictional features such as the barbs shown in the figure, or may benon-directional frictional features such as those of a textile. Fibrouselements 905 may be produced as a barbed monofilament, as a braidedtextile structure with frictional elements encased with the braid, as acombination barbed/braided structure, or as a textile or filament havinga roughened or high-friction surface.

The view of FIG. 9 is a section through a patient's neck showing thetongue T, lower mandible M, skin S, posterior pharyngeal wall PPW andpharyngeal airway PA. The fibrous elements 905 are passed through thepharyngeal wall from within the oral cavity with the two ends of theelements 905 entering a single hole located medially on the lateralaspect of the pharyngeal wall. In the placement, the retractor 900 maybe passed in an anterior/posterior orientation and exits the skin of theneck. A protective sheath similar to sheath 501 shown in FIG. 5 may beused to protect tissue during placement of the fibrous elements 905,particularly in the case where the tissue engaging element is anon-directional frictional feature. After placement, a central portion930 of the retractor engages tissue beneath the pharyngeal wall. Needles920 may be incorporated into the fibrous elements 905 to facilitateplacement.

The fibrous elements 905 are tensioned to retract the pharyngeal wall byproducing tension on tissue beneath the lateral pharyngeal wall, or atenting effect of the lateral wall if the elements are placed with aslight posterior/lateral and anterior/lateral angle during passage. Oncesufficient tension is applied, and the lateral wall is suspended, theends of the fibrous elements 905 are trimmed flush with the surface ofthe skin S and are allowed to retract slightly to remain in a sub-dermalposition. Alternatively, the retractor elements may be passed directlylaterally to exit the lateral tissue of the neck of the patient toprovide direct lateral suspension of the pharyngeal wall.

In another method of implantation, the pharyngeal retractors describedabove are implanted through an oral route. In its simplest embodiment,the method of implanting the device utilizes conventional surgicalinstruments such as a scalpel, forceps, etc with direct visualization ofthe pharyngeal wall though the mouth. Alternatively, the devices can beimplanted using a hand-held delivery system. FIG. 10 illustrates theapproach used to deliver one of the pharyngeal retractors previouslyillustrated in FIGS. 6 a-6 f. The hand-held delivery system 1000comprises a hand-piece 1090, a shaft 1091 extending therefrom, and ahousing 1092 on the distal end 1093 of the shaft 1091. The housing iscapable of holding at least one of the pharyngeal retractors 1094. Thepharyngeal retractors are held in the housing in a constrainedconfiguration.

The pharyngeal retractors are advanced out of the delivery system by adeployment means actuated by a lever 1097 on the hand-piece 1090. As thepharyngeal retractors are advanced out of the housing, they are deployedthrough a previously made incision in either the posterior or thelateral pharyngeal wall. Alternatively, the distal-most portion of thedelivery system may have a sharpened edge to facilitate penetration ofthe pharyngeal wall during deployment of the retractor 1094. Theretractors can then be set beneath the pharyngeal walls to provideconstant retraction of the airway.

FIGS. 11 a and 11 b illustrate the effect of implanting two of thedevices of the invention to alter the shape of the pharyngeal airway.The distance between the left lateral pharyngeal surface and the rightlateral surface is represented by distance A. The retractors 1120 areshown in FIG. 11 a in a constrained configuration, with a distance Bbetween the ends of each retractor which is greater than the distancebetween the ends of the unconstrained retractor. The retractor ismaintained in the constrained configuration with the tips 1121 a, 1121 bspread open within a delivery cannula or hollow stylus. The implantabledevice is passed into the tissues beneath the pharyngeal wall within apre-defined arc of the cannula or hollow stylus.

Upon termination of the stylus advancement, the implantable device isejected from the cannula or stylus by a pusher that maintains theimplantable device in a fixed position while the cannula/stylus iswithdrawn from the penetrated tissue beneath the pharyngeal wall.Effectively, the implantable device does not move; rather, the stylus iswithdrawn from around the implantable device. After deployment, theimplantable device returns to its unconstrained configuration with thetips 1121 a′, 1121 b′ of the retractors 1120′ contracting as shown inFIG. 11 b to the distance represented as B′, which is smaller thandistance B.

When the implantable device is placed in position beneath the pharyngealwall 1030, the tips 1121 a, 1121 b of the device engage the pharyngealwall so that the wall changes shape as the distance B between the tipschanges. For example, the tips may engage the pharyngeal wall bypinching a portion of the wall between them. In another example, thetips 1121 a, 1121 b may have barbs', hooks, roughening or another tissueengaging feature to maintain engagement of the tips with the pharyngealwall to exert a force on the wall.

After deployment of the two devices, the distance A between the lateralpharyngeal walls increases to A′, and the shape of the airway is alteredto produce two small irregular channels 1140, 1141 of decreased radiusof curvature in the pharyngeal wall 1130 parallel to the axis of theairway. The geometry of the channels is sufficiently small to preventthe relaxed tongue from forming a seal with the pharyngeal wall alongthose locations while a patient is in a sleeping state and themusculature of the tongue relaxes. While the tongue may seal with theposterior pharyngeal wall, the lateral aspects are maintained as openchannels 1140, 1141, effectively allowing air to flow past theobstruction.

In another embodiment of the invention shown in FIGS. 12 a and 12 b, twoimplantable devices 1220 are used to produce anterior-to-posteriorretraction of the pharyngeal airway to alter the shape of the airway.The distance between the anterior pharyngeal wall surface and theposterior pharyngeal wall surface is shown in FIG. 12 a as distance B.Similar to the embodiment discussed in FIG. 11, the implantable devicesare illustrated in FIG. 12 as deployed through the use of a deploymentcannula or hollow stylus. The cannula or hollow stylus has a curvedinterior having an arch shape with a radius smaller than a radius of theimplantable device in its free state. The device is essentially held ina constrained configuration within the cannula or stylus and is allowedto release during deployment. The ejection of the device from within thehollow cannula or stylus is again accomplished through the use of apusher that maintains the device in a fixed position as the cannula isretracted.

During ejection, the radius of the implantable device increases and thedistance between the tips of the device increases. Since theunconstrained devices 1220′ have a distance between the ends that isgreater than the distance between ends of the constrained devices, theanterior-to-posterior dimension B of the pharyngeal airway increases toB′, thereby changing the shape of the airway by increasing the radius ofcurvature of the wall, as shown in FIG. 12 b. In this embodiment, thebase of the tongue is also partially retracted from the edges of thetongue that abut the lateral location of the pharyngeal wall, the shapeof which has been altered through the use of the implantable devices.

While the implantable devices illustrated in FIGS. 11 and 12 are shownin the space beneath each of the lateral pharyngeal wall positions, asingle device 1320 may be placed beneath the posterior pharyngeal wall(PPW) in a concentric placement to the axis of the pharynx (PA), asshown in FIG. 13. In this position, the device alters the shape of bothlateral pharyngeal walls (LLPW & RLPW), thereby increasing the crosssectional area of the airway. Various length devices are feasibledepending upon the severity of the pharyngeal wall collapse duringsleep. In the case of pharyngeal wall collapse in the wakeful state, theimplantable device may be fabricated to expand upon insertion, similarto the retractor illustrated in FIG. 12, to provide additionalretraction during the awake state.

The devices, systems and surgical methods described above providesimple, minimally invasive procedures that may potentially be performedon an outpatient basis. Results of the procedures are both immediate andlong-term. The implanted devices do not impact the hyoid bone or softpalate, and are therefore less likely to affect swallowing or speech.The invention furthermore uses materials with a long-term history ofbiocompatibility.

The foregoing Detailed Description and accompanying figures are to beunderstood as being in every respect illustrative and exemplary, but notrestrictive, and the scope of the invention disclosed herein is not tobe determined from the Description of the Invention, but rather from theClaims as interpreted according to the full breadth permitted by thepatent laws. It is to be understood that the embodiments shown anddescribed herein are only illustrative of the principles of the presentinvention and that various modifications may be implemented by thoseskilled in the art without departing from the scope and spirit of theinvention.

1. A device for altering a shape of a pharyngeal wall by implantation ofthe device in tissue beneath the pharyngeal wall, the device comprising:a retracting element having a constrained configuration and anunconstrained configuration different from the constrainedconfiguration; and a tissue engaging element connected to the retractingelement, the tissue engaging element adapted for engaging the tissuebeneath the pharyngeal wall; whereby a shape of the pharyngeal wall isaltered when the retracting element reverts from the constrainedconfiguration to the unconstrained configuration.
 2. The device of claim1, further comprising: a trocar attached to at least one of theretracting element and tissue engaging element and having a shape forpositioning the retracting element and tissue engaging element in thetissue beneath the pharyngeal wall.
 3. The system of claim 2, furthercomprising: a plastic sleeve surrounding a distal end of the trocar, thedevice being attached to a proximal end of the plastic sleeve.
 4. Thesystem of claim 1, further comprising: a sheath covering at least aportion of the tissue engaging element for protecting non-target tissueas the device is implanted.
 5. The device of claim 1, wherein the tissueengaging element comprises a material selected from the group consistingof a medical textile and a perforated sheet.
 6. The device of claim 1,wherein the tissue engaging element comprises a tissue engaging featureselected from the group consisting of a barb, a projection, a velour anda hook element.
 7. The device of claim 1, wherein the retracting elementis comprised of a metal selected from the group consisting of nitinol,stainless steel, tantalum and titanium.
 8. The device of claim 1,wherein the retracting element comprises a flexible arch.
 9. The deviceof claim 1, wherein the retracting element and the tissue engagingelement are attached using an attachment selected from the groupconsisting of adhesives, sutures, clips, rivets, interweaving andenveloping.
 10. The device of claim 1, further comprising: an imageenhancing substance applied to the device, the substance selected fromthe group consisting of a radio-opaque substance and an echogenicsubstance.
 11. The device of claim 1, further comprising: a medicamentapplied to the device, the medicament selected from the group consistingof an anti-microbial, analgesic, anti-biotic, anti-inflammatory, andanti-pain medicament.
 12. A method for surgically treating obstructivesleep apnea, the method comprising the steps of: delivering animplantable device into tissue located beneath a pharyngeal wall; andengaging the tissue beneath the pharyngeal wall with the implantabledevice to alter a shape of the pharyngeal wall.
 13. The method of claim12, further comprising the step of: making one or more incisions in thepharyngeal wall.
 14. The method of claim 12, further comprising the stepof: changing a radius of curvature of a portion of the pharyngeal wall.15. The method of claim 12, further comprising the step of: inducingtissue ingrowth into the implantable device.
 16. The method of claim 12,wherein the delivering step further comprises: introducing theimplantable device orally and through the pharyngeal wall into thetissue beneath the pharyngeal wall.
 17. The method of claim 12, whereinthe delivering step further comprises the steps of: penetrating thepharyngeal wall with a trocar; and manipulating the trocar to deliverthe device into the tissue beneath the pharyngeal wall.
 18. The methodof claim 12, wherein the delivering step further comprises: positioninga distal end of a hand-held delivery system proximate the pharyngealwall, the hand-held delivery system containing at least one implantabledevice in a constrained state; and actuating a lever of the hand-helddelivery system to deploy the implantable device into the tissue beneaththe pharyngeal wall, the implantable device assuming an unconstrainedstate having a different shape from the constrained state.
 19. Themethod of claim 12, wherein the implantable device includes a protectivesheath surrounding at least a portion of the device; the method furthercomprising the step of: removing the sheath to permit the implantabledevice to engage the tissue beneath the pharyngeal wall.
 20. A systemfor treating obstructive sleep apnea by altering a shape of a pharyngealwall, the system comprising: an implantable device comprising a tissueengaging element and a retracting element; and a hand-held deliverysystem comprising a hand-piece, an actuating lever moveably connected tothe hand-piece, a shaft extending distally from the hand-piece, ahousing disposed at a distal end of the shaft for storing at least oneimplantable device, and a deployment device activatable by the lever fordeploying the implantable device through the pharyngeal wall into tissuespace located beneath the pharyngeal wall so as to alter a shape of thepharyngeal wall.
 21. The system of claim 20, wherein the implantabledevice has a constrained state, and an unconstrained state having adifferent shape from the constrained state; and wherein the housingdisposed at the distal end of the shaft is for storing the at least oneimplantable device in the constrained state.
 22. The system of claim 21,wherein the implantable device comprises an arch-shaped member havingtwo ends, and wherein a distance between the ends changes as theimplantable device changes from the constrained state to theunconstrained state.
 23. The system of claim 20, wherein the distal endof the hand-held delivery system further comprises: a sharp edge forcreating an incision in the pharyngeal wall through which theimplantable device is deployed.
 24. A device for retracting a pharyngealwall, the device comprising: an elongate fibrous member having a centralportion for engagement with tissue beneath the pharyngeal wall, andhaving first and second retracting portions extending from the centralportion, each of the first and second retracting portions havingfeatures for engaging tissue in the neck and exerting a tensileretraction force on the central portion.
 25. The device of claim 24,wherein the elongate fibrous member comprises a monofilament and thefeatures for engaging tissue in the neck and exerting a tensileretraction force on the central portion comprise barbs.
 26. The deviceof claim 24, further comprising: a needle attached to a distal end of atleast one of the retracting portions for passing the retracting portionthrough the tissue in the neck.